US20090155090A1

US20090155090A1 - Auxiliary electrodes for enhanced electrostatic discharge

Info

Publication number: US20090155090A1
Application number: US12/336,427
Authority: US
Inventors: Daniel J. Schlitz
Original assignee: VENTIVA
Current assignee: VENTIVA
Priority date: 2007-12-18
Filing date: 2008-12-16
Publication date: 2009-06-18
Also published as: TW200938727A; EP2229686A1; JP2011511997A; WO2009079538A1; CN101896990A; KR20100116173A

Abstract

In general, the present invention relates to methods and apparatuses that achieve high gas flow rates through the use of an electrostatic pump. According to some aspects, the present invention relates to additional, auxiliary electrodes that generate increased ion current at lower voltages, which leads to greater pumping power than a corona wind discharge. According to further aspects, the invention provides for a directional emission of the ions. This eliminates the back flow of ions and improves the electro-fluid power conversion efficiency and pumping performance. According to yet further aspects, the invention enables the electrodes to be fabricated directly on a dielectric substrate, making the system mechanically rugged and easily fabricated.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to U.S. Prov. Appln. No. 61/014,694 filed Dec. 18, 2007, the contents of which are incorporated by reference herein in their entirety.

FIELD OF THE INVENTION

The present invention relates to electrostatic pumping apparatuses and methods using ion generation, and more particularly, to enhanced corona discharge using novel electrode arrangements for establishing the ion generation zone without relying on small features of a corona electrode to concentrate the electric field.

BACKGROUND

An electrostatic hydrodynamic (EHD) gas pump such as a corona discharge gas pump (i.e. corona wind) typically consists of one or more sharp (e.g. corona) and blunt (e.g. collecting or neutralizing) electrodes. An electric field is applied between the two electrodes causing a partial breakdown of the gas, referred to as a corona discharge, near the sharp electrode. The discharge produces ions which are attracted to the neutralizing, or collecting electrode. En route, the ions collide with neutral gas molecules creating pressure head and flow similar to that produced by a mechanical fan. Co-pending application Ser. Nos. 11/338,617, 12/017,986 and 12/011,219, commonly owned by the present assignee, and the contents of which are incorporated herein by reference, have dramatically advanced the state of the art of EHD pumps and cooling apparatuses incorporating the same, including those that utilize corona wind techniques.
Some attempts have been made to enhance corona discharge through various electrode arrangements. One example is U.S. Pat. No. 5,019,709, titled “Electrode arrangement for cheating [sic] corona.” This patent discloses an electrode arrangement for creation of a corona over an area. The arrangement includes a corona driving portion and a corona emitting portion in electrical contact with the corona driving portion. The corona driving portion is much larger in size than the corona emitting portion such that corona from the electrode arrangement is emitted from the corona emitting portion in a direction away from the corona driving portion. The corona emitting portion is comprised of a series of stepped, generally concentric, spaced corona emitting rings about a center emitting element. The locations of the rings and emitting element are such that a corona is produced over a circular area rather than an annular ring. This invention is a complex corona electrode that consists of multiple ionization regions.
Another attempt is U.S. Pat. No. 7,053,565, titled “Electrostatic fluid accelerator for and a method of controlling fluid flow”. This patent discusses issues of “back flow” with regards to multi-stage electrostatic pumps. Their solution is to synchronize the waveforms on the corona electrodes.
There also are a large number corona discharge publications and patents concerning a variety of two-electrode geometries and applications. There is also a large body of literature regarding Dielectric Barrier Discharge (DBD). However, none of this literature discusses utilizing the DBD to enhance a corona discharge current.
Accordingly, a need remains in the art for improved electrostatic discharge current, including methods and apparatuses that do not rely on complex electrode geometries or waveform schemes, among other things.

SUMMARY

In general, the present invention relates to methods and apparatuses that achieve high gas flow rates through the use of an electrostatic pump. According to some aspects, the present invention relates to additional, auxiliary electrodes that generate increased ion current at lower voltages, which leads to greater pumping power than a corona wind discharge. According to further aspects, the invention provides for a directional emission of the ions. This eliminates the back flow of ions and improves the electro-fluid power conversion efficiency and pumping performance. According to yet further aspects, the invention enables the electrodes to be fabricated directly on a dielectric substrate, making the system mechanically rugged and easily fabricated.
In furtherance of these and other aspects, an electrostatic hydrodynamic apparatus according to embodiments of the invention includes one or more auxiliary electrodes disposed near a primary sharp electrode in a sharp/blunt electrode pair, wherein the electrode pair is configured such that when an electric field is applied between them, a partial breakdown of the gas between them occurs near the primary sharp electrode, which produces ions that are attracted to the blunt electrode, and wherein electric power applied to the one or more auxiliary electrodes is applied independently of the electric field applied to the electrode pair.
In additional furtherance of these and other aspects, an electrostatic hydrodynamic apparatus according to embodiments of the invention includes a primary sharp electrode, a blunt electrode integrally formed in a fin of a heat sink, one or more auxiliary electrodes disposed near the primary sharp electrode, wherein the primary sharp and blunt electrodes are configured such that when an electric field is applied between them, a partial breakdown of the gas between them occurs near the primary sharp electrode, which produces ions that are attracted to the blunt electrode, and wherein the one or more auxiliary electrodes are configured to enhance the ion production.
In yet additional furtherance of these and other aspects, a heat sink according to the invention includes a plurality of separated fins and an electrostatic hydrodynamic (EHD) apparatus comprising: a primary sharp electrode, a plurality of blunt electrodes integrally formed in respective ones of the fins, one or more auxiliary electrodes disposed near the primary sharp electrode, a voltage source coupled to the primary sharp and blunt electrodes for establishing an electric field between them, and an auxiliary voltage source coupled to the one or more auxiliary electrodes, wherein the auxiliary voltage source is controlled independently from the voltage source so as to enhance ions produced between the primary and blunt electrodes.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures, wherein:

FIGS. 1A and 1B show perspective and end views, respectively of the primary/auxiliary electrode system and collector electrodes of example embodiments of the invention;

FIG. 2 illustrates an example self seeding mechanism according to embodiments of the invention;

FIG. 3 shows an example plasma mechanism according to embodiments of the invention;

FIGS. 4(A) and 4(B) illustrate how primary/auxiliary electrodes according to the invention can cause ions to be generated in a desired direction, resulting in better pumping efficiency.

FIG. 5 illustrates a recessed substrate that is used to confine the direction of the ion current according to embodiments of the invention;

FIG. 6 illustrates an alternative embodiment where a primary electrode is placed directly in between the auxiliary and collector electrodes; and

FIG. 7 illustrates an alternative embodiment showing wire-like primary and auxiliary electrodes.

DETAILED DESCRIPTION

The present invention will now be described in detail with reference to the drawings, which are provided as illustrative examples of the invention so as to enable those skilled in the art to practice the invention. Notably, the figures and examples below are not meant to limit the scope of the present invention to a single embodiment, but other embodiments are possible by way of interchange of some or all of the described or illustrated elements. Moreover, where certain elements of the present invention can be partially or fully implemented using known components, only those portions of such known components that are necessary for an understanding of the present invention will be described, and detailed descriptions of other portions of such known components will be omitted so as not to obscure the invention. Embodiments described as being implemented in software should not be limited thereto, but can include embodiments implemented in hardware, or combinations of software and hardware, and vice-versa, as will be apparent to those skilled in the art, unless otherwise specified herein. In the present specification, an embodiment showing a singular component should not be considered limiting; rather, the invention is intended to encompass other embodiments including a plurality of the same component, and vice-versa, unless explicitly stated otherwise herein. Moreover, applicants do not intend for any term in the specification or claims to be ascribed an uncommon or special meaning unless explicitly set forth as such. Further, the present invention encompasses present and future known equivalents to the known components referred to herein by way of illustration.
According to one aspect, the present invention provides a unique ion generation mechanism. This method and apparatus establishes the ion generation zone without relying on small features of a corona electrode to concentrate the electric field. In addition, the quantity of ions generated is enhanced.
In general, embodiments of the invention include a set of auxiliary electrodes in close proximity to a primary electrode as shown in FIGS. 1A and 1B. More particularly, FIG. 1A is a perspective view of the primary/auxiliary electrode system and collector electrodes 106 and FIG. 1B is a detailed view of the primary 102 and auxiliary electrodes 104 provided on a common substrate 108 when the system is viewed from an end.
As shown in FIG. 1B, in operation, the auxiliary electrodes 104 stimulate the ionization region which surrounds the primary electrode 102. As will be described in more detail below, the electrodes 104 can be configured to either increase production of seed electrons for ion generating electron avalanches or be used to generate a weak plasma. In the latter case, the plasma is confined to the small region surrounding the primary electrode 102 because the electric field strength in the gap between the primary/auxiliary electrodes and the large grounded electrode 106 is too weak to sustain a plasma.
In some embodiments, the sizes of the primary electrode 102 and auxiliary electrodes 104 are about 5 to 250 μm wide and the auxiliary electrodes 104 are separated by about 5 to 250 μm from the primary electrode 102. In such configurations, the gap from the primary/auxiliary electrode system to the large, collector electrodes 106 range from about 0.25 to 5 mm and the voltages applied between the primary electrode 102 and collector electrode 106 range from about 0 to 5000 V. Many variations are possible, as will become apparent to those skilled in the art after being taught by these examples. Substrate 108 is typically implemented using a dielectric material such as quartz, glass, metal-oxides, polymers, etc.
Moreover, as shown in FIG. 1A, collector electrodes 106 are contoured and configured as fins of a heat sink as described in more detail in co-pending application Ser. No. 12/017,986. However, this is not necessary, and many other configurations and electrode geometries are possible.
In general, the auxiliary electrodes can be held between 0 and 5000 V, independent of the primary and ground electrodes. For example, lowering the voltage applied to the auxiliary electrodes towards ground potential, raising the voltage above the primary electrode voltage or oscillating the auxiliary electrode voltage stresses the ionization region to the point of breakdown, a state with a very large number of free electrons and ions. A plasma arc can be avoided through the use of a current limiting resistor, replacing the resistor with a capacitor, or by coating the auxiliary electrodes with a dielectric. This process generates more ions than a corona discharge, which is limited by the process of seed electron production.
One advantage of configuring the auxiliary electrodes of the present invention is that it produces more ions at a lower voltage than a corona discharge. This results in more pumping power and a greater pressure head. This can be accomplished in several different ways, as illustrated in more detail in connection with FIGS. 2 and 3. Generally, FIG. 2 shows an example embodiment employing self seeding mechanism where large amounts of seed electrons are provided by the auxiliary electrodes and initiate additional avalanches in the high electric field region near the primary electrode. FIG. 3 shows an example plasma mechanism where the auxiliary electrodes generate a plasma in the region surrounding the primary electrode. The plasma is the ion source for the enhanced corona discharge.
More particularly, in the example embodiment shown in FIG. 2, the auxiliary electrodes 104 provide seed electrons to the system. This self-seeding mechanism is in contrast to a corona discharge, where seed electrons come from the ground electrode or through photo-ionization of gas molecules. Seed electron production is the limiting factor in corona discharges. This embodiment of the invention decouples the seed electron current from other gaseous electronic properties of the system, and hence it can be independently controlled and enhanced. The seed electron current, in this embodiment of the present invention, is controlled primarily by the voltage waveform V_auxon the auxiliary electrodes 104 and by geometrical design considerations. This seed electron current determines the ion current. Larger seed electron currents create larger ion currents, which leads to a more effective pump (larger pumping action and larger pressure head).
As described above, R_auxis provided in this configuration to limit current and to thereby prevent plasma formation. In one example configuration, where auxiliary electrodes 104 are 25 mm across and separated by 25 mm, V_auxis 500 V and R_auxis 10 MΩ.
Alternatively, as shown in FIG. 3, the auxiliary electrodes 104 can be used to establish a weak plasma in the region near the primary electrode 102. In this embodiment, the plasma is the source of an enhanced ion current. Then, similar to the self-seeding electron process, a large ion current emanates from these electrodes that exceeds any corona process. In one example configuration, where auxiliary electrodes 104 are V_auxis 500 V.
Another advantage of the invention is that the ion production can be confined to a region that lies between the primary/auxiliary electrodes and the collector electrode. This is illustrated in more detail in connection with FIGS. 4(A) and 4(B). For example, FIG. 4A illustrates an example configuration of a corona discharge pump 410 that generates ions in all directions, some of which counteract the desired overall pumping action and/or direction of air flow.
FIG. 4(B) illustrates a configuration made possible by the present invention in which a substrate 402 has mounted thereon primary/auxiliary electrodes 102/104 which only generate ions in the desired direction, resulting in better pumping efficiency. In this configuration, the ions can only travel in a direct path towards the ground electrode 106. There is no counter-current and no counter-acting pumping forces as in the configuration of FIG. 4(A). As a result, the electro-fluidic power conversion efficiency of primary/auxiliary electrodes is higher.
FIG. 5 illustrates another possible configuration in which a recessed substrate 508 is used to confine the direction of the ion current. More particularly, the directional confinement of the ion current is not limited to 180°. It can directed in an arbitrarily narrow beam as shown in FIG. 5 by recessing the primary/ auxiliary electrodes 102 and 104 in an shrouded substrate 508. It can also be opened up to exceed 180°, and many other variations are possible by varying the geometry of the substrate 508.
Many configurations of primary and auxiliary electrodes according to the principles of the invention are possible other than those described above. Two of the many possible additional embodiments of the invention are shown below in FIGS. 6 and 7. They represent further implementations of the same basic concept of primary-auxiliary ion generator as described in the present application.
FIG. 6 illustrates an alternative embodiment where the primary electrode is placed directly in between the auxiliary and collector electrodes. More particularly, FIG. 6 shows a device where the primary electrode 102 is positioned between a single, large auxiliary electrode 604 formed in a substrate 608 and a collector electrode (not shown).
FIG. 7 illustrates an alternative embodiment showing wire-like electrodes. More particularly, this diagram also shows an embodiment where there is a gap between the primary and the dielectric. In the example of FIG. 7, both primary electrode 702 and auxiliary electrode 704 are implemented as wire-type electrodes. This figure also depicts an option where the primary electrode 702 is offset from the substrate 708 in which auxiliary electrode 704 is provided, leaving an air gap between the electrodes.
In one example implementation, the corona discharge configurations and methodologies described herein can be utilized as an electrostatic air pump. For example, the primary/auxiliary electrodes can be integrated into a heat sink to create a complete cooling system or they can be used as a stand-alone air blower.
It should be further noted that in the present invention, it is no longer required to have a small diameter corona electrode to create the high electric field ionization region as in many conventional approaches. With auxiliary electrodes of the present invention, the high electric field region is created by the primary and the auxiliary electrodes. Since the gap can be larger than is possible with a corona discharge wire, the corona electrode can be made less sensitive to dust build-up. Dust accumulation on a corona electrode immediately reduces the pumping performance due to an increase in the effective size of the corona electrode. Dust accumulation on the self seeding electrodes will not have the same effect, since the ion generation region is no longer defined by the size of the primary electrode.
Although the present invention has been particularly described with reference to the preferred embodiments thereof, it should be readily apparent to those of ordinary skill in the art that changes and modifications in the form and details may be made without departing from the spirit and scope of the invention. It is intended that the appended claims encompass such changes and modifications.

Claims

1. An electrostatic hydrodynamic (EHD) apparatus comprising:

one or more auxiliary electrodes disposed near a primary sharp electrode in a sharp/blunt electrode pair,

wherein the electrode pair is configured such that when an electric field is applied between them, a partial breakdown of the gas between them occurs near the primary sharp electrode, which produces ions that are attracted to the blunt electrode,

and wherein electric power applied to the one or more auxiliary electrodes is applied independently of the electric field applied to the electrode pair,

and wherein the one or more auxiliary electrodes are configured to direct the produced ions in a desired direction.

2. An EHD apparatus according to claim 1, wherein the one or more auxiliary electrodes are configured to provide seed electrons for an electron avalanche near the primary sharp electrode.

3. An EHD apparatus according to claim 1, wherein the one or more auxiliary electrodes are configured to establish a weak corona near the primary sharp electrode.

4. (canceled)

5. An EHD apparatus according to claim 1, wherein the one or more auxiliary electrodes are disposed in an upstream direction from the primary sharp electrode with respect to the desired direction.

6. An EHD apparatus according to claim 1, wherein the blunt electrode is integrally formed in a fin of a heat sink.

7. An EHD apparatus according to claim 1, wherein the blunt electrode has a contoured edge facing the primary sharp electrode.

8. An electrostatic hydrodynamic (EHD) apparatus comprising:

a primary sharp electrode;

a blunt electrode integrally formed in a fin of a heat sink; and

one or more auxiliary electrodes disposed near the primary sharp electrode,

wherein the primary sharp and blunt electrodes are configured such that when an electric field is applied between them, a partial breakdown of the gas between them occurs near the primary sharp electrode, which produces ions that are attracted to the blunt electrode,

and wherein the one or more auxiliary electrodes are configured to enhance the ion production.

9. An EHD apparatus according to claim 8, wherein the one or more auxiliary electrodes are configured to provide seed electrons for an electron avalanche near the primary sharp electrode.

10. An EHD apparatus according to claim 8, wherein the one or more auxiliary electrodes are configured to establish a weak corona near the primary sharp electrode.

11. An EHD apparatus according to claim 8, wherein the one or more auxiliary electrodes are configured to direct the produced ions in a desired direction.

12. An EHD apparatus according to claim 8, wherein the blunt electrode has a contoured edge facing the primary sharp electrode.

13. An EHD apparatus according to claim 8, wherein the primary sharp electrode and one or more auxiliary electrodes are disposed on a common substrate.

14. An EHD apparatus according to claim 13, wherein the substrate is contoured to partially shroud the primary sharp electrode and one or more auxiliary electrodes so that ion current is constrained in a desired direction.

15. An EHD apparatus according to claim 13, wherein the substrate is substantially flat with opposing surfaces and wherein the primary sharp electrode is disposed on an opposite surface from the one or more auxiliary electrodes.

16. An EHD apparatus according to claim 8, wherein the primary sharp electrode is comprised of a wire, and wherein the one or more auxiliary electrodes comprises a conductor surrounded by a dielectric disposed substantially parallel to the primary sharp electrode.

17. A heat sink, comprising:

a plurality of separated fins; and

an electrostatic hydrodynamic (EHD) apparatus comprising:

a primary sharp electrode,

a plurality of blunt electrodes integrally formed in respective ones of the fins,

one or more auxiliary electrodes disposed near the primary sharp electrode,

a voltage source coupled to the primary sharp and blunt electrodes for establishing an electric field between them, and

an auxiliary voltage source coupled to the one or more auxiliary electrodes,

wherein the auxiliary voltage source is controlled independently from the voltage source so as to enhance ions produced between the primary and blunt electrodes.

18. A heat sink according to claim 17, wherein the one or more auxiliary electrodes are configured to provide seed electrons for an electron avalanche near the primary sharp electrode.

19. A heat sink according to claim 17, wherein the one or more auxiliary electrodes are configured to establish a weak corona near the primary sharp electrode.

20. A heat sink according to claim 17, wherein the one or more auxiliary electrodes are configured to direct the produced ions in admired direction.